# HelmValve¶

This is a steam power generation turbine model for the stages between the inlet and outlet.

## Example¶

from pyomo.environ import ConcreteModel, SolverFactory, TransformationFactory

from idaes.core import FlowsheetBlock
from idaes.power_generation.unit_models.helm import HelmValve
from idaes.generic_models.properties import iapws95
from idaes.ui.report import degrees_of_freedom, active_equalities

solver = SolverFactory('ipopt')
solver.options = {'tol': 1e-6}

m = ConcreteModel()
m.fs = FlowsheetBlock(default={"dynamic": False})
m.fs.properties = iapws95.Iapws95ParameterBlock()
m.fs.valve = HelmValve(default={"property_package": m.fs.properties})

hin = iapws95.htpx(T=880, P=2.4233e7)
# set inlet
m.fs.valve.inlet.enth_mol[0].fix(hin)
m.fs.valve.inlet.flow_mol[0].fix(26000/4.0)
m.fs.valve.inlet.pressure[0].fix(2.5e7)
m.fs.valve.Cv.fix(0.01)
m.fs.valve.valve_opening.fix(0.5)
m.fs.valve.initialize(outlvl=1)


## Variables¶

This model adds a variable to account for mechanical efficiency to the base PressureChanger model.

Variable

Symbol

Index Sets

Doc

Cv

$$C_v$$

None

Valve coefficient for liquid [mol/s/Pa^0.5] for vapor [mol/s/Pa]

valve_opening

$$x$$

time

The fraction that the valve is open from 0 to 1

## Expressions¶

Currently this model provides two additional expressions, with are not available in the pressure changer model.

Expression

Symbol

Index Sets

Doc

valve_function

$$f(x)$$

time

This is a valve function that describes how the fraction open affects flow.

## Constraints¶

The pressure flow relation is added to the inherited constraints from the PressureChanger model.

If the phase option is set to "Liq" the following equation describes the pressure-flow relation.

$\frac{1}{s_f^2}F^2 = \frac{1}{s_f^2}C_v^2\left(P_{in} - P_{out}\right)f(x)^2$

If the phase option is set to "Vap" the following equation describes the pressure-flow relation.

$\frac{1}{s_f^2}F^2 = \frac{1}{s_f^2}C_v^2\left(P_{in}^2 - P_{out}^2\right)f(x)^2$

## Initialization¶

This just calls the initialization routine from PressureChanger, but it is wrapped in a function to ensure the state after initialization is the same as before initialization. The arguments to the initialization method are the same as PressureChanger.

## HelmValve Class¶

class idaes.power_generation.unit_models.helm.valve_steam.HelmValve(*args, **kwds)
Parameters
• rule (function) – A rule function or None. Default rule calls build().

• concrete (bool) – If True, make this a toplevel model. Default - False.

• ctype (class) – Pyomo ctype of the block. Default - pyomo.environ.Block

• default (dict) –

Default ProcessBlockData config

Keys
dynamic

Indicates whether this model will be dynamic or not, default = useDefault. Valid values: { useDefault - get flag from parent (default = False), True - set as a dynamic model, False - set as a steady-state model.}

has_holdup

Indicates whether holdup terms should be constructed or not. Must be True if dynamic = True, default - False. Valid values: { useDefault - get flag from parent (default = False), True - construct holdup terms, False - do not construct holdup terms}

material_balance_type

Indicates what type of mass balance should be constructed, default - MaterialBalanceType.useDefault. Valid values: { MaterialBalanceType.useDefault - refer to property package for default balance type **MaterialBalanceType.none - exclude material balances, MaterialBalanceType.componentPhase - use phase component balances, MaterialBalanceType.componentTotal - use total component balances, MaterialBalanceType.elementTotal - use total element balances, MaterialBalanceType.total - use total material balance.}

energy_balance_type

Indicates what type of energy balance should be constructed, default - EnergyBalanceType.useDefault. Valid values: { EnergyBalanceType.useDefault - refer to property package for default balance type **EnergyBalanceType.none - exclude energy balances, EnergyBalanceType.enthalpyTotal - single enthalpy balance for material, EnergyBalanceType.enthalpyPhase - enthalpy balances for each phase, EnergyBalanceType.energyTotal - single energy balance for material, EnergyBalanceType.energyPhase - energy balances for each phase.}

momentum_balance_type

Indicates what type of momentum balance should be constructed, default - MomentumBalanceType.pressureTotal. Valid values: { MomentumBalanceType.none - exclude momentum balances, MomentumBalanceType.pressureTotal - single pressure balance for material, MomentumBalanceType.pressurePhase - pressure balances for each phase, MomentumBalanceType.momentumTotal - single momentum balance for material, MomentumBalanceType.momentumPhase - momentum balances for each phase.}

has_phase_equilibrium

Indicates whether terms for phase equilibrium should be constructed, default = False. Valid values: { True - include phase equilibrium terms False - exclude phase equilibrium terms.}

has_pressure_change

Indicates whether terms for pressure change should be constructed, default - False. Valid values: { True - include pressure change terms, False - exclude pressure change terms.}

property_package

Property parameter object used to define property calculations, default - useDefault. Valid values: { useDefault - use default package from parent model or flowsheet, PropertyParameterObject - a PropertyParameterBlock object.}

property_package_args

A ConfigBlock with arguments to be passed to a property block(s) and used when constructing these, default - None. Valid values: { see property package for documentation.}

has_work_transfer

True if model a has work transfer term.

has_heat_transfer

True if model has a heat transfer term.

valve_function

The type of valve function, if custom provide an expression rule with the valve_function_rule argument. default - ValveFunctionType.linear Valid values - { ValveFunctionType.linear, ValveFunctionType.quick_opening, ValveFunctionType.equal_percentage, ValveFunctionType.custom}

valve_function_callback

This is a callback that adds a valve function. The callback function takes the valve bock data argument.

phase

Expected phase of fluid in valve in {“Liq”, “Vap”}

• initialize (dict) – ProcessBlockData config for individual elements. Keys are BlockData indexes and values are dictionaries described under the “default” argument above.

• idx_map (function) – Function to take the index of a BlockData element and return the index in the initialize dict from which to read arguments. This can be provided to overide the default behavior of matching the BlockData index exactly to the index in initialize.

Returns

(HelmValve) New instance

## HelmValveData Class¶

class idaes.power_generation.unit_models.helm.valve_steam.HelmValveData(component)[source]

Basic adiabatic 0D valve model. This inherits the balance block to get a lot of unit model boilerplate and the mass balance, enegy balance and pressure equations. This model is intended to be used only with Helmholtz EOS property pacakges in mixed or single phase mode with P-H state vars.

Since this inherits BalanceBlockData, and only operates in steady-state or pseudo-steady-state (for dynamic models) the following mass, energy and pressure equations are implicitly writen.

1. Mass Balance:

0 = flow_mol_in[t] - flow_mol_out[t]

2. Energy Balance:

0 = (flow_mol[t]*h_mol[t])_in - (flow_mol[t]*h_mol[t])_out

3. Pressure:

0 = P_in[t] + deltaP[t] - P_out[t]

build()[source]

Add model equations to the unit model. This is called by a default block construnction rule when the unit model is created.

initialize(outlvl=0, solver=None, optarg=None)[source]

For simplicity this initialization requires you to set values for the efficency, inlet, and one of pressure ratio, pressure change or outlet pressure.